Re: [Evolution] 3.16.3: Failed to refresh folder "INBOX",

[Pete Biggs <pete biggs org uk>]

On Wed, 2015-06-24 at 16:59 +0100, Patrick O'Callaghan wrote:
> On Wed, 2015-06-24 at 10:38 +0100, Pete Biggs wrote:
> > > command-line ping, dig, or host command returns the new IP for a 
> > DNS
> > > name, Evolution should be using that as well.

[[I wish they would fix this line wrapping of quoted content ...]]

> > Not necessarily, it depends on the individual libraries being used.
>
> Strictly that is true, but one would expect a reasonably configured
> system to use a single resolver library for everything. Usually that is
> libresolv.so, which is part of glibc.

No, that's just not so, it's much more complex than that.  Most user
programs, like ping, use routines like 'gethostbyname' (or their more
modern equivalent) - those routines get their information from a
variety of sources - /etc/hosts, YP/NIS, DNS - which ultimately might
use libresolv.  Gnome applications tend to use the GIO libraries.  And
DNS querying programs like nslookup, host and dig go directly to the
DNS server.

Things are complicate further by systems such as nscd - "Name Service
Cache Daemon" that, as it says in the man page, "provides a cache for
the most common name service requests" - and that includes hosts.  The
default TTL for hosts in nscd is 1 hour.

That's why I said in reply to the original poster that you need to be
careful about using things like nslookup to verify DNS entries since
other parts of the system may be caching previous results.

P.